Apparatus and method for thermal connection of optical waveguides

ABSTRACT

A splicer comprises a positioning device, in which the fiber ends in general have a residual offset. A memory stores a predetermined relationship between the possible offset and a parameter which controls the application of heat. The parameter which controls the application of heat, for example the splicing time for a predetermined splicing current, is defined on the basis of an actual offset which can be recorded by means of cameras.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/EP07/060,602 filed Oct. 5, 2007, which claims the benefit ofpriority to German Application No. 102006047425.2, filed Oct. 6, 2006,both applications being incorporated herein by reference.

BACKGROUND

1. Field

The disclosure relates to the field of connection of optical waveguides.The disclosure relates in particular to an apparatus in order to connectends of optical waveguides to one another by means of a thermal process.The disclosure also relates to a corresponding method.

2. Technical Background

Apparatus for connection of optical waveguides by means of theapplication of heat are generally known. In the case of splices such asthese, the fiber ends of the optical waveguides to be spliced areheated, as a result of which they can be fused to one another. In thiscase, it is desirable for the resultant attenuation of the splicedconnection to be as low as possible. A different amount of effort isrequired for this purpose, depending on the apparatus type, for examplebecause the fiber ends to be spliced are aligned with respect to oneanother and the splicing process is matched to the circumstancesresulting from the environment, in order to ensure that the attenuation,resulting from the spliced connection, for the light propagating in thefiber is as low as possible. By way of example, an arc, a coronadischarge, a laser beam or a resistance wire in the form of a heatingfilament, for example, can be used to melt the fiber ends.

Recently, there has been a demand for splicers which can be produced atlow cost and are as reliable during operation as possible, are simple tooperate and require little maintenance in use while neverthelesscomplying with demands that are as stringent as possible for the qualityof the resultant spliced connection. Apparatus such as these are used,for example, for installation of optical waveguides in buildings or forconnection of the buildings by optical waveguides to the existingnetwork. Apparatus such as these have characteristics including lowweight, mechanical and electronic elements in the apparatus which are assimple and robust as possible, and as high a degree of automation aspossible for the production of the spliced connection.

By way of example, WO 2007/019843 describes a splicer which useselectromechanical motors, for example stepping motors, for alignment ofthe fiber ends, as well as mechanical step-down conversion. The steppingmotors and the step-down conversion are available at lost cost, althoughcompromises must be accepted in the positioning accuracy of thesemechanical elements. In the case of a splicer such as this, a residualoffset generally remains when viewed in a direction at right angles tothe longitudinal axis of the optical waveguides. Exact alignment of thefibers can be achieved only by chance, and a residual offset generallyremains, because of the restricted accuracy of said positioning device,in the order of magnitude of approximately 1 micrometer (μm). In thecase of apparatus such as these, the welding process is carried out witha fixed welding current and a fixed welding time. This setting wasdefined as being optimum just for one typical initial offset, as aresult of which initial offset values which differ from this are nottreated individually. In particular, no matching of the weldingparameters is carried out.

Conventional splicers, for example as described in U.S. Pat. No.6,230,522, use an offset reduction in order to adjust the apparatus andits splicing parameters to match a splicing environment, and retainunchanged the parameter set, which is then defined, for control of thenext splicing process and further splicing processes. To this end, adefined distance is set between the fibers to be connected for a testsplice, the fiber ends are heated, and any remaining residual offset ofthe connected fibers is determined. A relationship which indicates acurrent correction as a function of a remaining residual offset can bestored in the apparatus. These apparatus therefore require complexrecording and alignment electronics as well as complex mechanicalelements in order to always ensure that the optical waveguides arealigned with respect to one another as accurately as possible and asreproducibly as possible at the start of the normal splicing process. Byway of example, complex positioning systems such as these use piezoelements based on piezoelectric ceramics, which allow the cores of theglass fibers to be welded to be positioned on two axes.

It is therefore desirable to nevertheless make it possible to produce ahigh-quality spliced connection using a splicer of the type mentionedinitially, which can achieve only relatively inaccurate positioning ofthe ends of the optical waveguides.

SUMMARY

In one embodiment, an apparatus for thermal connection of respectiveends of at least two optical waveguides has: in each case onepositioning device which is associated with one of the opticalwaveguides and by means of which the ends are moved relative to oneanother to a position which allows a connection produced by theapplication of heat; an observation device, by means of which anyrelative offset of the ends of the optical waveguides to be connected isdetermined; a memory, by means of which a predetermined relationship isproduced between a possible offset and a parameter which controls theapplication of heat; a thermal device by means of which the ends of theoptical waveguides are connected as a function of a value which isemitted from the memory.

The apparatus accepts an initial residual offset between the opticalwaveguide ends to be spliced. Corresponding positioning elements can beprovided for positioning of the fiber ends, which positioning elementshave grooves into which the fiber ends are placed. The grooves can befixed in position relative to one another. It is also possible to carryout a certain rough alignment of the fiber ends, with the positioningaccuracy nevertheless being, for example, in the range from more thanabout 1 μm up to 10 μm, such that a lateral offset can be expectedbetween the fiber ends.

The apparatus now records the offset of the external contours of theoptical waveguides according to the exemplary embodiment, before theoptical waveguides are welded to one another, and then determinesoptimum control for one or more parameters of the splicing process, onthe basis of a predetermined relationship which is stored in theapparatus. By way of example, when using a splicer with an arc or coronadischarge, the welding time, for example the operating time, duringwhich the arc is active, is defined as a function of the determinedoffset, using the relationship stored in the apparatus. Additionally orelse alternatively, the current level for supplying the arc electrodescan be adjusted.

In one embodiment, a desired attenuation which is required for thespliced connection to be produced is fixed on the apparatus, for exampleat the manufacturer's premises or else adjustably by the user. Theapparatus then determines the optimum welding time automatically fromsaid relationship stored in the apparatus memory and on the basis of ameasured offset between the optical waveguides, before the connectionprocess. By way of example, various relationships which are eachassociated with one desired attenuation to be preset are stored in theapparatus and are activated as appropriate by the manufacturer or theoperator, on the basis of the preset. Different attenuations requiredifferent welding current levels, so that the temporarily storedrelationships are configured on the basis of the attenuation and/or onthe basis of the welding-current level. This can mean that oneassociated relationship of said type is stored for each givenwelding-current level.

The stored predetermined relationship between any possible offsetbetween the external contours of the still unconnected opticalwaveguides before they have been welded and the splicing parameter,which is selected as a function of this, for example the supply currentlevel for the heating device of the splicer, may be stored in the formof a look-up table or in the form of a calculation rule, for example acalculation formula, for instance in the form of an equation for astraight line, or some other mathematical curve. By inputting thecurrently measured fiber offset, it is possible to directly determinethe parameter on the basis of which one of the possible storedrelationships was defined, for example in advance by presetting adesired attenuation.

According to one embodiment, a method for thermal connection ofrespective ends of at least two optical waveguides comprises:positioning of the ends of the at least two optical waveguides relativeto one another so as to allow a connection by the application of heat;recording of an image of the ends of the at least two opticalwaveguides; determination of any offset between the ends of the at leasttwo optical waveguides; output of a value for a parameter from a memory,which provides a relationship between any possible offset and aparameter which influences the application of heat; operation of a heatsource as a function of the value for the parameter, in order to connectthe ends of the at least two optical waveguides.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will be explained in more detail in the following textwith reference to one exemplary embodiment, which is illustrated in thefigures of the drawing. Mutually corresponding elements in the variousfigures are provided with the same reference signs.

FIG. 1 shows an outline circuit diagram of major elements of a spliceraccording to one embodiment.

FIG. 2 shows a detailed illustration of the ends of two opticalwaveguides to be connected.

FIG. 3 shows an illustration in order to explain the relationship,stored in the apparatus in FIG. 1, between the offset and the weldingtime.

FIG. 4 shows various relationships which are provided for differentwelding currents.

FIG. 5 shows a representative illustration for the relationship which isstored in the apparatus shown in FIG. 1.

DETAILED DESCRIPTION

The splicer illustrated in FIG. 1 is used to connect the ends of twooptical waveguides 100, 101, which may be optical fibers, to one anotherby thermal influence. A corona discharge zone or arc zone 303 isproduced for this purpose, which melts the mutually opposite ends of theoptical waveguides. The optical waveguides are moved toward one anotherand are thus connected. By way of example, the optical waveguides areglass fibers with one or more cores that carry light. The fiber end 100originates from an optical waveguide 105 which is surrounded by a sheath102, which has been removed at the end 100 in such a way thatessentially all that is present there is the fiber core 107, whichcarries the light, surrounded by the glass sheath 106 with differentrefractive index (FIG. 2). The end of the other optical waveguide 101 isconstructed in a corresponding manner. All known types of opticalwaveguides are suitable for use as optical waveguides, but in particularmonomode fibers or NZDS fibers (non-zero-dispersion shifted fibers). Theoptical waveguides may be optical fibers such as glass fibers.

Positioning devices 201, 202 have respective grooves 203 and 204 inwhich the fiber ends are placed. The positioning elements 201, 202 andtherefore the grooves 203, 204 can be fixed largely exactly in positionin the apparatus in one embodiment. These grooves are then preferablyaligned largely exactly with respect to one another. The V-shapedgrooves may, for example, be ground in ceramics or else etched insilicon, and are thus aligned with respect to one another by theproduction process to within fractions of micrometers. Nevertheless, themutually opposite surfaces 110, 111 of the fiber ends to be connected toone another may be offset with respect to one another, for examplebecause the fibers can have a different diameter and are thereforelocated at a different height in the normally V-shaped groove. On theother hand, the fiber ends may be dirty, or the grooves may becontaminated with dust particles. In addition, frozen-in stresses in oneof the fibers or forces exerted on the fibers by hold-down mechanismscan lead to an offset and to a position situation as illustrated in FIG.2. Finally, it is possible for the fiber ends not to have been insertedcompletely exactly parallel to the groove surfaces within the groove.

There is generally also an offset between the fiber ends to be weldedwhen the positioning elements 201, 202 are not fixed completely but canbe moved relative to one another by means of a movement device whichoffers only a rough adjustment capability which, for example, is in therange of greater than 1 micrometer (μm). The positioning devices 201,202 may be designed as in DE 102005038937.6, and may have anelectrically powered stepping motor which produces a movement capabilityin the x-direction by means of a spindle or some other step-uptransmission from the motor revolution. The connection comprisingspindle/transmission and stepping motor currently in principle has arelatively high positioning accuracy, although this is less accuratethan the positioning accuracy which can be achieved by a piezoceramicand is in the order of magnitude from about 0.06 μm to 0.1 μm. Saidstepping motor mechanical elements provide a positioning accuracy of 1μm in the lowest case, and typically from 5 to 6 μm.

The splicer in FIG. 1 now has a respective camera in the x direction andy direction, 401 and 402, by means of which the surrounding area withinthe corona discharge zone 303 can be recorded in the form of an image.By way of example, the cameras 401, 402 are charged coupled devices(CCD) which record an image resolved into pixels, and provide thisdigitally. Respective light sources 411, 412 are associated with the CCDarrays 401 and 402 and illuminate the corona discharge zone 303.

The cameras 401, 402 produce respective position images 403 and 404which are evaluated in a control system 407 for the splicer, whichcontrol system is handled, for example, by a microprocessor. Normally,position images of the fiber ends are recorded from two differentdirections. In FIG. 1, these are the x-direction and the y-direction,which are at an angle of 90 degrees to one another. The directions mayalso include a different angle. Furthermore, it is possible to use onlyone camera and, by means of appropriate optics, for example mirroroptics which direct light beams produced by the light sources 411, 412at the corona discharge zone 303 such that images of the fibers ends arerecorded from two different directions by said one of the cameras. Forexample, one of the images is recorded in one part of the camera, andthe other one of the images in another part of the camera. Appropriateoptics are sufficiently well known to a person skilled in the art andthey will therefore not be explained in any more detail here.

The splicer also has a movement device 205 which can create a movementalong the z-direction of the fibers, that is to say in the fiberlongitudinal direction 206. This is necessary when the welding processis already taking place and the fused ends of the optical waveguides arepushed into one another during the welding process in order to produce acertain overlap and to compensate for material loss as a result of theheating process, or lack of glass material as a result of the endsurfaces not being ideal. The positioning accuracy along the direction206 is relatively uncritical to the accuracy.

A value for a parameter, which drives the respective electrodes 301 and302 via couplings 304, 305 is now determined, as will be described inmore detail further below, on the basis of the images 403, 404 of thefiber ends within the corona discharge zone 303, with these images beingtransmitted along the operative connection 405, 406 to the processor 407of the splicer. When a corona discharge or an arc is being used to weldthe fiber ends 100, 101, the amount of current, for example the timeperiod for which the current is supplied, from the current which issupplied to the electrodes 301, 302 is controlled via the couplings 304,305. The supplied current is converted via the corona discharge or thearc that is produced by the electrodes 301, 302 to an amount of heatwhich is available for welding the fiber ends. The greater the amount ofheat, the better the fibers, which are offset in their positionsrelative to one another on the x-y plane, will be matched to one anotherduring the welding process, because of the self-centering effect.Ideally, there is no longer any offset on completion of the weldingprocess, or the offset is so small that a desired resultant attenuationof the light propagation in the optical waveguide is achieved, or adefined maximum attenuation is undershot. If, for example, a constantpredetermined current level is set, the time period during which thecurrent is supplied, that is to say the welding time, is controlled bythe couplings 304, 305.

In principle, the optimization can be carried out in different steps.From experience, an appropriately suitable current level is required inorder not to exceed a desired maximum attenuation of the splicedconnection to be produced. The current level of the electrodes 301, 302is therefore defined by defining the desired maximum attenuation at theconnection 413, which the completed spliced connection should achieve orundershoot. The input of the maximum attenuation at the connection 413can be defined once in the factory, or can be defined as required by theoperator of the apparatus by means of a manual input. The controlinformation for the operative connections 304, 306 and the splicing timeis then provided by the relationships stored in the control device 407,on the basis of the offset that can be determined in the images 403,404.

In the apparatus shown in FIG. 1, the offset D1 of the external contours108, 109 of the optical fiber ends 100, 101 is determined as illustratedwith reference to FIG. 2. Since the apparatus determines the offset fromtwo different directions, for example the x-direction and they-direction, which are offset at an acute angle, preferably at 90degrees to one another, a total offset, derived from this, is defined.For example, if the observation directions are offset at 90 degrees toone another, the total offset is determined by forming the root of thesum of the squares of the measured offset values associated with the xand y directions. Each image of the fiber ends recorded by a cameracomprises an image of the fiber ends resolved into pixels so that, forexample, the offset D1 between the external contours 108, 109 can bedefined by a gray-scale evaluation and counting of pixels. During thewelding process, the residual offset D1 is partially or completelycompensated for by the self-centering effect of the material forces andsurface forces.

In addition, it should be mentioned that the fibers also have an offsetD2, which runs in the z-direction, between the end faces 110, 111 of theoptical waveguides. This offset is compensated for during the weldingprocess by the z-positioning device 205, even with an overlap of thefiber ends being produced.

The relationship between the fiber offset and the welding time as storedin the control device 407 can be represented as illustrated in FIG. 3.The horizontal axis 501 represents the possible values to be expected inpractice for the fiber offset, while a correspondingly associatedwelding time can be read from the vertical axis 502. The illustratedrelationship is shown in the form of a curve, in this case a straightline 503, which was determined as a regression line on the basis of theindividual measured or empirical values 504 a, 504 b, 504 c, etc. Thepresent fibers to be welded are, for example, fibers of the SMF 1528type with an eccentricity of 0.1 μm, from Corning, Incorporated. Thestraight line 503 was determined for a welding current of 14.0 mA. Thisallows a certain desired attenuation of the spliced connection to beachieved or undershot. A different desired maximum intended attenuationmay require a different welding current. The straight line which isassociated with a different welding current such as this in general hasa different vertical position and a different grading than the straightline illustrated in FIG. 3. For example, a regression line determined onthe basis of the measured values for a welding current of 13.0 mA isabove the straight line 503 in the graph and has a greater gradient thanthe straight line 503. The optimum welding time can be determined, onthe basis of the fiber offset determined in any given specific case, onthe basis of that straight line which is associated with the desiredattenuation or the predetermined current. The fiber offset measured atany given time is used as an input value, and the welding time isdetermined on the basis of the straight line, and is emitted as anoutput value.

The illustrated straight lines are determined on the basis of initialexperiments. This is done using a splicer in which a predeterminedoffset can be set between the fibers. The predetermined offset is set,and the integrated auto fusion time control can in this case determinethe respective optimum welding time. The averaged optimum welding timeswhich result in the lowest attenuation being achieved are associatedwith the corresponding offset values at intervals of 1.0 μm, as values504 a, 504 b, . . . , 504 c (FIG. 3). The regression line 503 isdetermined from this.

FIG. 4 shows various relationships for a different welding current. Thestraight line 503 in FIG. 4 corresponds to the straight line 503 in FIG.3. The straight line 505 is intended for a splicing current of 13.0 mA.The straight line 506 is intended for a welding current of 15.0 mA. Ascan be seen, the optimum welding time of 3 seconds for a welding currentof, for example, 14.0 mA is increased to about 5 seconds if the fiberoffset is increased from 0 μm to 6 μm. The lengthening of the optimumwelding time is greater when using a reduced welding current of 13.0 mA.The straight line 505 is therefore above the straight line 503, that isto say when using higher values for the welding time, compared with thestraight line 503. A fiber offset of 6 μm results in a welding time of 9seconds with a welding current of 13.0 mA.

In principle, a further reduction in the attenuation of the completedspliced connection can be achieved with a reduced welding current, inparticular when the fiber offsets are relatively large. A furtherreduction in the attenuation such as this for relatively large fiberoffsets is associated with the welding time being lengthened.Conversely, the use of a higher splicing current with large fiberoffsets leads to greater attenuation. A specific attenuation thresholdvalue is therefore defined in one embodiment, which is intended to beachieved for the splices. The attenuation value is entered in theapparatus via the connection 413.

The welding current must be set in an appropriate manner in order toachieve or undershoot a maximum permissible splice attenuation. Forexample, an attenuation is entered by the operator at the connection413, or is permanently programmed in the factory, for one application. Asuitable welding current for achieving a predetermined maximumattenuation depends on the initially found offset between the fibers. Ingeneral, it is better to use a high welding current when the offset isrelatively small, and to use a lower welding current when the offset isgreater. A higher welding current at the same time reduces the weldingtime. It is thus possible to define a specific attenuation thresholdvalue which is intended to be achieved for all splices. If an initialoffset is now determined for which the desired attenuation cannot beachieved with the currently selected welding current, a differentwelding current is set as appropriate, and another of the relationshipsillustrated in FIG. 4 is therefore chosen, and the resultant weldingtime is determined from this, as a result of which the predeterminedmaximum attenuation value is achieved or undershot. For example, thiscontrol process may comprise a high splicing current being set for lowinitial offset values, a medium splicing current being set for mediumoffset values, and a splicing current which is lower than this being setfor high offset values. Summarized in a look-up table, this results in:

Offset Welding current ≦5 μm 15.0 mA 6 . . . 7 μm 14.0 mA ≧8 μm 13.0 mAThe required welding time is determined in a corresponding manner fromthe curves illustrated in FIGS. 3 and/or 4. In order to achieve or toundershoot a maximum predetermined attenuation, a control characteristicis used for which the splicing current to be set decreases in steps as afunction of the initial offset found.

In practice, the relationship as illustrated in an idealized form inFIG. 3 is stored in the control device 407, in a memory 420 that isprovided there, for example as a table as illustrated in FIG. 5.Corresponding tables (not illustrated separately) are stored in thememory 420 for the curves 505, 506 in FIG. 4. By way of example, thememory 420 contains different discrete input values 0 . . . 10 with theunit being μm, each of which is associated with a respective weldingtime of 3.0 . . . 6.2, with seconds (s) as the unit. The relationshipneed not necessarily be a straight line 503 as illustrated in FIG. 3. Itmay be a curve of any desired higher order, or a curve definedcompletely on the basis of empirical values. An interpolation process isrequired when the offset as determined from the images 403, 404 isbetween two stored values for the fiber offset.

As an alternative to the relationship illustrated in FIG. 5, acalculation rule can also be stored in the memory 420, in an equivalentform. In the present case, the calculation rule, which corresponds tothe relationship illustrated in FIG. 5:Welding time (in s)=0.32 s/μm×fiber offset (in μm)+3.0 sis used (s: seconds). Corresponding calculation rules are respectivelypossible for the curves 505, 506.

In the exemplary embodiment, the respective said total offset isdetermined from the respective images 403 and 404 recorded along thex-direction and along the y-direction, and this is used as an inputvariable for the relationship stored in the memory 420, where it is usedeither as an input value for the table (left-hand column in FIG. 5) oras an input value for the calculation rule, as a result of which awelding time can be determined from this, in seconds. The control device407 and the couplings 304, 305 switch on the welding current at a levelof, for example, 14.0 milliamperes (mA) for connection of SMF 1528optical fiber ends to the electrodes 301, 302 during this welding time.If the initial offset found, or a value which represents the initialoffset, is signaled as an input value to the memory, the welding time,or a value which represents the welding time, will be emitted from thememory, as a function of this, in the described exemplary embodiment.

The memory 420 stores a multiplicity of relationships which can beassociated with different welding currents. One of these relationshipsis selected for the described control process as a function of thepresetting of a desired welding current.

In other embodiments, a laser device, for example with a laser diode,can be used instead of the described electrodes 301, 302 in order toproduce an arc or a corona discharge. A laser beam is produced and isdeflected by means of optics such that it supplies thermal power to thesplice point, thus allowing the fiber ends to be welded. In thissituation, using a predetermined current for the laser, the operatingtime of the laser is determined on the basis of the relationship storedin the memory 420, using the residual offset found between the fibers tobe spliced. It is also possible to use a heating filament in a so-calledfilament splicer, which comprises a resistance filament which producesan amount of heat which is sufficient to connect the fiber ends to oneanother by melting. The operating time during which the current issupplied through the heating filament in order to produce heat islikewise determined from the relationship stored in the memory 420 forthe current which is defined by a predetermined attenuation.Alternatively, it is also possible to set both the current and thewelding time, that is to say the time for which the current is supplied,on the basis of the relationship stored in the memory 420 and on thebasis of the determined offset. In general, the invention comprises thedetermination of a residual offset on the basis of the images of thefiber ends recorded by the cameras 401, 402 and the determination of aparameter, which controls the application of heat in the splicing zone,in general on the basis of a relationship which is stored in the memory420.

The described exemplary embodiment shows a pair of fibers 100, 101 whichare to be connected to one another. The concepts disclosed are likewiseapplicable to ribbon splicers in which, instead of the individual fibers100, 101, ends of fiber ribbons which, for example, may comprise four,six, eight or twelve pairs of fibers, are welded to one another.Appropriate evaluation methods are known for this purpose, in order touse the cameras 401, 402 to determine the offset between the ends of twofiber ribbons to be welded. In the present example, the maximum offsetwhich occurs among all of the pairs of fibers that are respectively tobe connected within the ribbons is determined in order then to determinethe optimum welding time from the maximum offset value on the basis ofthe relationship stored in the memory 420. Alternatively, an averageoffset of all the offset values measured between the pairs of fibers inthe two ribbons to be welded can also be used. The averaging process canbe carried out by forming an arithmetic mean value, a geometric meanvalue or a suitably weighted mean value.

An additional attenuation reduction can be achieved by pulses. For thispurpose, the arc is struck repeatedly in a pulsed form, in a processwhich follows the splicing process that has been described so far. Theattenuation can be further improved by producing a predetermined numberof current pulses for corresponding arc effects. It is important todefine the optimum number of pulses, with the time interval between thepulses and the duration of the individual pulses being of secondaryimportance to the improvement of the attenuation. The appropriatelydefined number of current pulses are produced as a function of theinitial fiber offset. With a fiber offset of 1.5 μm, two welding currentpulses are additionally also suitable to further reduce the attenuationof the resultant spliced connection, in addition, after the weldingprocess using the optimum welding time according to one of the curvesfrom FIGS. 3 to 5. By way of example, three pulses are required for aninitial offset of 3 μm. The pulse current is 16.0 mA, the pulse durationis 3 seconds, and the pause time duration between two pulses is 0.2seconds, in the exemplary embodiment. This attenuation reduction methodis particularly advantageous for a splice connection of so-called NZDSfibers (non-zero-dispersion shifted fibers).

The disclosure is applicable in particular to splicers in which thefiber ends are positioned with a residual offset which cannot becompensated for. The splicing process is carried out in an automatedform and in this case produces an optimized spliced connection with thelowest possible attenuation.

1. An apparatus for thermally connecting respective ends of at least twooptical waveguides, comprising: in each case a positioning device whichis associated with one of the optical waveguides and by means of whichtheir ends are moved relative to one another to a position which allowsa connection produced by the application of heat, the positioning devicebeing roughly adjustable with respect to another positioning device,transversely with respect to a longitudinal direction of the opticalwaveguides, with a positioning accuracy which is greater than one (1)micrometer, for aligning the ends of the optical waveguides to less thansix (6) micrometers of a residual offset; an observation device, bymeans of which a possible offset of the ends of the optical waveguidesto be connected is determined; a memory, by means of which apredetermined relationship is provided between the possible offset, thepredetermined relationship being a combination of lateral and axialoffset stored within the memory, the predetermined relationship defininga value; and a parameter which controls the application of heat by athermal device by means of which the ends of the optical waveguides areconnected as a function of the value which is output from the memory,wherein the parameter is selected from the group consisting of a supplycurrent of the thermal device, an amount of heat produced by the thermaldevice, an operating time period of the thermal device, and combinationsthereof, wherein the application of heat from the thermal device, ascontrolled by the parameter, more closely aligns the optical waveguidesas the optical waveguides are connected and compensates for the residualtransverse offset.
 2. The apparatus of claim 1, the positioning deviceincluding an electrically powered stepping motor.
 3. The apparatus ofclaim 1, wherein the positioning devices which can be associated withthe optical waveguides have a respective groove into which in each caseone section of the optical waveguide to be connected is placed.
 4. Theapparatus of claim 1, wherein the positioning devices are fixed inposition relative to one another.
 5. The apparatus of claim 1, whereinthe memory contains a stored table in which the relationship betweenvalues of the possible offset of the ends of the optical waveguides anda parameter is stored.
 6. The apparatus of claim 1, wherein the memorycontains a calculation rule which provides a relationship between valuesof the possible offset of the ends of the optical waveguides and aparameter.
 7. The apparatus of claim 1, wherein the memory contains aplurality of said relationships, with each of said relationships beingassociated with a different attenuation, and an input device is providedfor an attenuation value which the complete connection is intended toachieve or undershoot.
 8. The apparatus of claim 1, wherein the memorycontains a plurality of said relationships, with each of therelationships being associated with a different supply current of thethermal device, and with one of the relationships being selected.
 9. Theapparatus of claim 1, wherein the thermal device has a pair ofelectrodes by means of which an arc or a corona discharge is produced inorder to melt and to connect ends of the optical waveguides, with acontrol device controlling the current which is supplied to the pair ofelectrodes, and/or the time period during which the current is suppliedto the pair of electrodes in order to form an arc or a corona discharge.10. The apparatus of claim 1, wherein the thermal device is a laserdevice which produces a laser light beam in order to melt and to connectthe ends of the optical waveguides, with the control device controllinga current which is supplied to the laser device, and/or the time periodduring which the laser devices is supplied with a current to form thelaser light beam.
 11. The apparatus of claim 1, wherein the thermaldevice is a heating resistance device whose current level or currentsupply time is controlled by the control device.
 12. The apparatus ofclaim 1, wherein the observation device comprises at least one camera inorder to record an image of the ends of the at least two opticalwaveguides transversely with respect to the longitudinal axis of theoptical waveguides.
 13. The apparatus of claim 12, wherein at least twocameras are provided in order to record the at least two images of theends of the at least two optical waveguides from at least two differentdirections transversely with respect to the longitudinal axis of theoptical waveguides.
 14. The apparatus of claim 1, wherein theobservation device determines the offset of the external contours of theoptical waveguides from one direction or from at least two differentdirections.